Synthetic turf systems have been used for some sports traditionally played on natural turf, or grass. Natural grass surfaces tend not to stand up well to wear and generally require a great deal of maintenance. Also, the grass of the natural turf surface typically does not grow well in partly or fully enclosed sports stadiums. Overall, synthetic grass surfaces stand up to wear much better than the natural grass surfaces, do not require as much maintenance, and can be used in closed stadiums.
Some synthetic grass surfaces comprise rows of strips, ribbons, or fibers of synthetic material extending vertically from a backing mat with a particulate material—infill or infill layer—located between the ribbons and above the mat. The infill material assists in supporting the synthetic ribbons in a generally upright orientation. In addition, the infill may contribute to the resiliency of the synthetic turf system and aid in its overall drainage. Commonly used components for the infill includes hard particulate matter, e.g., sand; soft particulate matter, e.g., rubber; and, various combinations thereof. In applications requiring additional drainage or resiliency, the backing mat may be placed over a drainage tile or resilient pad, respectively.
The synthetic fibers represent blades of grass that are relatively soft and non-abrasive and are typically constructed of polypropylene or polyethylene. A portion of the synthetic ribbons extends a predetermined distance above the infill layer of particulate material and provides the synthetic turf system with a more grass-like appearance. The exposed ends of the synthetic ribbons can also provide a desired amount of friction to, among other things, a rolling ball used in baseball, soccer, lacrosse, etc. In some situations when the exposed ends of the synthetic fibers are bent or folded over, the coefficient of friction of the synthetic fiber relative to the rolling ball is reduced, and thus the ball will roll at a speed that may be relatively faster than that expected when rolling over a natural grass surface.
After the installation or use of a playing surface comprising a synthetic turf system, it is not uncommon to find a portion—perhaps a significant portion—of exposed synthetic ribbons to be bent or folded over instead of remaining relatively upright. Although folded or bent synthetic ribbons may not be objectionable for use in some events, there are other events such as high-level soccer where it would be undesirable.
Earlier designs of synthetic turf systems have focused on providing synthetic ribbons having a desired length, rigidity, and spacing for a particular sporting event. As such, the playing surface was not adaptable to other events having dissimilar playing characteristics. Depending on the desired playing characteristics for a sporting event, the corresponding physical characteristics of the associated synthetic ribbons may be different. For instance, it may be preferable in one sport as compared to another sport for the ball to roll over the synthetic grass surface at a faster or slower speed. As such, it would be beneficial if the physical characteristics of the synthetic ribbons could be adjusted depending upon the desired playing characteristics of the sporting event or the playing level of the participants. Thus, instead of the synthetic ribbon having a “fixed” amount of rigidity and relative friction, these characteristics could be altered. In situations where different events are held on the playing surface, some of the events may reluctantly be played on a synthetic turf surface that may have less than optimal playing characteristics for that particular sporting event.
Accordingly, the present invention is directed to a novel method of altering the physical characteristics of a synthetic playing surface dependent upon the desired playing characteristics of the event. In particular, the present invention is directed to stiffening at least a portion of the exposed ends of the synthetic fibers, when desired, so that the stiffened ends stay in a relatively upright orientation for a predetermined period of time.
The present invention is provided to address these and other considerations.